Means for producing oscillations



June 2, 1925. 1,540,578

. H. C. THOMPSON MEANS FOR PRODUCING OSCILLATIONS Filed July 1, 1921[rm/enter Hay-ivy; CgThom son,

by His Attorney.

Patented June 2, 1925.

- UNIT En STATES PATENT oer-"ice.

HARRY C. THOMPSON, O'F' SCHEIJEGTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORIE'QRATION OYF NETW $503K.

MEANS FOR PRODUCING OSCILLATIDNS.

Application filed July 1,

To allwhom it may concern:

Be it known that I, HARRY Cl THOMPSON, a citizen of the United States,residing at Schenectady, county of Schenectady, State of New York, haveinvented certain new and useful Improvements in Means for ProducingOscillations, of which the following is a specification.

My present invention. relates to means for producing oscillatorycurrents and more particularly to-the application oi? electron dischargeapparatus for this purpose.

The object oi my invention'is to provide a simple and: eiiicientarrangement for producing oscillatory currents by means of an electrondischarge device of the dynatron or negative resistance type.

A more specific object of my invention is to provide an. improvedcircuit arrangement for producing oscillatory currents by. means of asystem and apparatus of the, general type described in Hull Patent1,313,188 of August 12, 1-919.

In that patent an electron discharge device is described having anelectron emitting cathode and two other electrodes enclosed in. anevacuated receptacle. Sources of potential are applied between thecathode and the other electrodes of such value that a sufficientemission of secondary or impact electrons will be' effected from. one ofthe other electrodes to produce a negative resistance characteristic inthe circuit between the cathode and that electrode. This circuit is anoscillatory ci roi'iit and it the resistance is of the proper value withrespect to the inductance and capacity of the circuit oscillatorycurrents will automatically be produced therein the frequency oi whichwill be determined by the constants of the circuit. The alternatingcurrents produced may be supplied to a utilization circuit by couplingan inductance in the utilization circuit to the inductance of theoscillatory circuit.

It is now known that the oscillatory currents; producedby such anarrangement may equally well be supplied to a utilization circuit bycoupling such circuit to. the circuit between the cathode and theelectrode which receives the impact electrons from the elec' trode bywhich they are emitted. In such case the amount of energy whichcirculates inthe oscillatory circuit may be very small,

1921-; Serial No. 481,979.

as. all that the oscillatory'energy has to accomplish is to vary thepotential of the electrode to which. it is connected with. respectto'the cathode. In the arrangement shown in: the Hull patent referredto, the average potential of this electrode with respect to the cathodeis maintained positive by the use of a direct current sourceof potentialhaving its positive ternrinal connected to the electrode which emitsimpact electrons, and its negative terminal connected tothe oathode. Ihave discovered, however, that when the utilization circuit is. coupledto the circuit of the electrode which receives the impact electrons,greater efliciency in operation may be obtained by maintaining theaverage potential of the electrode which emits impact electrons negativewith respect to the cathode.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims. My inventionitself, however, both as to its organization andmethod of operation willbest be understood by reference. to the following description taken inconnection with the accompanying drawing in which. I have indicateddiagrammatically one circuit organization whereby my invention may becarried into effect.

As shown inthe drawing, I provide an electron discharge device 1 havingan electron emitting cathode 2, a second electrode 3 and a thirdelectrode at, which is interposed between the cathode 2 and theelectrode 'lhis electrode 4 may be in the form of a grid or it may bemade in any other desired form of construction which will permit of thepassage ofelectrons between the cathode 2 and elect-rodeB, and will alsobe capable of producing a desired electrostatic field between thoseelectrodes. The electrode 3 is maintained at a fairly high positivepotential with respect to the cathode 2 by means of a direct currentsource 5, which is included in. the circuit between these electrodes.The value of the potential. required will depend largely on theconstruction. of the device. In some cases itmay be'as low as 300 voltswhile for other devices potentials as high as 1000 volts'may benecessary. The circuit between cathode 2 and electrode 3 is anoscillatory circuit which comprises. in-

be supplied to the circuit.

from the description set forth in Hull Patent 1,313,188. It will beapparent that when oscillations are produced in the oscillatory circuitthe potential of electrode 4 with respect to that of cathode 2 willalternately become more positive or more negative than normal. When theelectrode 4 is negative With respect to the cathode no electrons will bereceived thereby and no energy will be supplied to the oscillatorycircuit. hen it is positive with respect to the cathode it will receiveelectrons therefrom and energy will As it becomes more positive theimpactelectrons will be emitted from the electrode 4 in sufficientnumber. so that the net current flowing to the electrode 4 will reversein direction. All that is necessary in order to maintain the oscillatorycurrent in the circuit is that the energy supplied to the circuit whenthe direction of the current reverses, will be some-v what greater thanthe energy supplied to the circuit before the current reverses in direction.

The interval of time required to supply to the circuit the energynecessary tomaintain oscillations may be short in comparison with theperiod of the oscillations. It is therefore possible to maintain theelectrode 4 at a negative potential with respect to the cathode during agreater portion of the time than that during which it is positive, and Ihave found that in a system such as that illustrated more etficientresults may be obtained when the average potential of the electrode 4with respect to the cathode is maintained negative, as by means of thedirect current source 8. All that is necessary to start the productionof oscillations in the system described is to give to the electrode 4 inany suitable manner a momentary positive charge, and when the productionof oscillations is once started in this way it will be automaticallymaintained by reason of the fact that the potential of the electrode 4will alternately become positive and negative with respect to thecathode 2.

It will be evident that the current flowing in the circuit between thecathode 2 and electrode 3 whether-it be considered as produced mainly bymeans of electrons emitted from the cathode 2 or by the combination ofsuch electrons with the impact electrons emitted from the electrode 4will vary in accordance with the variations in the potential of electrode 4. It is therefore apparent that the current in this circuitbetween cathode 2 and electrode 3 will pulsate and that oscillationsof'the same frequency as those set up in the circuit 6, 7 may besupplied by means of a coupling transformer 9 to a utilization circuit10 of any form desired.

.VVhile I have shown and described the simplest embodiment of myinvention it will be apparent that my invention is by no means limitedto the particular embodiment shown but that many modifications inthetype of apparatus employed as well as in the circuit connections usedmay be made without departing from the scope of my invention asset forthin the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is,-

1. Means for producing oscillations comprising an electron dischargedevice having an electron emitting cathode and at least two otherelectrodes, an oscillatory circuit connecting the cathode and one of theother electrodes, a circuit connecting the cathode and a secondelectrode and containing a source of potential of such value as topermit of the effective emission of impact electrons from the firstelectrode in sufficient amount to produce a negative resistancecharacteristic in the circuit connected thereto over a range of positivepotential of the first electrode, and means for maintaining the averagepotential of the first electrode negative with respect to the cathode.

2. Means for producing oscillations comprising an electron dischargedevice having an electron emitting cathode and at least two otherelectrodes, an oscillatory circuit connecting the cathode and one of theother electrodes, a circuit connecting the cathode and a secondelectrode and containing a source of potential of such value as topermit of the effective emission of impact electrons from the firstelectrode in sufficient amount to produce a negative resistancecharacteristic in the circuit connected thereto over a range of positivepotential of the first electrode, and a source of direct currentpotential included in the circuit between the cathode and the firstelectrode having its positive terminal connected to the cathode.

3. Means for producing oscillations comprising an electron dischargedevice having an electron emitting cathode and at least two otherelectrodes, an oscillation circuit connected between the cathode and oneof the other electrodes, means for producing an emission of impactelectrons from the electrode to which the oscillatory circuit isconnected suflicient to produce a negative resistance characteristic inthat circuit over a range of positive potential of the electrodeconnected to the oscillatory circuit, and means for maintaining theaverage potential of the electrode to which the oscillatory circuit isconnected negative with respect to the cathode.

4. Means for producing oscillations co1nprising an electron dischargedevice having an electron emitting cathode and at least two otherelectrodes, an oscillation circuit connected between the cathode and oneof the other electrodes, ieans for producing an emission of impactelectrons from the 1 electrode to which the oscillatory circuit isconnected sufiicient to produce a negative resistance characteristic inthat circuit over a range of positive potential of the electrodeconnected to the oscillatory circuit, and a source of direct currentpotential included in the oscillatory circuit having its positiveterminal connected to the cathode. a?

In Witness whereof, I have hereunto set my hand this 30th day of June,1921.

HARRY C. THOMPSON.

